we have experimented with different power supplies for use with the Raspberry Pi 3B (plus and normal). Most of them exceed the power needed by the Raspberry Pi, i.e. 5V and 3A for example, or 5v and 2.5A, but many result in a warning in the “Device” page of Info beamer telling us that the power is not enough.
Have you got any suggestion as to a verified power supply for Pi 3+? Should we stick with the “Official” one which is quite expensive? Could it be a problem of the cable, or maybe of overheating since the Raspberry is inside an enclosed metal case?
Can’t really help with a power supply suggestion, but give a bit more insight on where that warning is coming from: info-beamer OS regularly checks the output of vcgencmd get_throttled. See this forum post for a description of the return value. When the under-voltage has occurred flag is set the system triggers the warning on the device dashboard. According to the post, this happens when the voltage drops below 4.63V (from the 5V that is supposed to be supplied).
Overheating (at least for the Pi itself) is probably not the reason for this and even gets an extra flag (throttling has occurred) that is only triggered if the Pi processor exceeded 85°C. You can check out the temperature for the last 24 hours on the device page. Even when enclosed, the Pi is probably not above 70°C.
Thanks. So we’ll keep experimenting with various power supply. And thanks for the technical insight.
Regarding temperature, it’s always around 50 degrees, so it’s not because of this,
I’m not sure that’s a good idea. The warning is there for a reason. Under-voltage can result in random crashes or other problems. It’s there to help you realize that there is something wrong with your hardware setup that might cause problems. How are you powering your Pis?
I agree with @infobeamer-fw, but maybe we can think of another info, along the warning: the number of times the alarm was raised in the last 24h? Or since the last reboot. This can give the measure of how often the problem arises.
For me it’s very mysterious, it appears both on a Raspberry Pi3+ (more power hungry) and a less powe hungry Raspberry Pi3…
And the power supplies are oversized… maybe the quality is not so good.
[…] the number of times the alarm was raised in the last 24h?
That would indeed be helpful, but I’m not that can be implemented. Right now the OS is querying the under-voltage has occurred (bit 16) flag. This flag is set once when the Pi detects an under-voltage condition. It is never reset and requires a reboot AFAIK. The other flag is under-voltage (bit 0). This is only set while the Pi detects under-voltage. I don’t think there is any other way than to poll this flag. This obviously can result in the system missing this condition depending on the polling interval. Right now the check just calls vcgencmd get_throttled every two minutes and is guaranteed to catch this condition as it uses bit 16. For a polling approach, calling vcgencmd every seconds wouldn’t work and we’d have to find out how get this status in a more direct way.